Compilation of life tables data of Hippodamia variegata Geoze (Coleoptera: Coccinellidae) when raized on Aphis gossypii Glover (Homoptera: Aphididae) using three different crops

Abstract

This study shows the life table of the predator Hippodamia variegate during the period January – March 2004. The predator was collected from Alfa alfa forage field at Shambat Demonstration Farm. The predators were confined with a number of aphids in cylindrical cages 9 cm in diameter covered with a piece of cloth held in position by a mean of rubber band. Eggs of the predator were collected at frequent times for the study purposes. A cohort of predator eggs (200 eggs) were placed on leaves of okra, eggplant and potato crops to follow-up and record the life table data until the adult stage. From the emerged adults, ten males and ten females were selected and confirmed each pair separately to follow the rest of the life table's data. The average net rate of reproduction (Ro) was (182.245), time generation (T) was (17.61), the innate capacity for numerical increase (rm) was (0.296) and the doubling generation time (DT) was (2.331) in potato crop. In okra crop the (Ro) was (145.29), (T) was (16.593), (rm) was (0.3) and (DT) was (2.3). In eggplant the (Ro) was (122.631), (T) was (18.698), (rm) was (0.257), and (DT) was (2.68). The highest (mx) was recorded in okra leaves and the lowest in eggplant. The female longevity (Lx) was high in okra crop (0.5) compared to value obtained from the potato crop (0.140). 3 Following the development of the immature stages, the mortality rates were found to be 40 %, 24 %, 15 % and 12 % among the eggs, larvae, pupae, and adult stages respectively. From these results, the highest death rate was mainly recorded among the immature stages. Highest rate of egg laying was recorded in Datura leaves (31.66 eggs) followed by Ushar leaves (30.1 eggs) and lastly pumpkin leaves (20 eggs). The field surveys of population, A. gossypii and the predator H. variegate was carried out in three vegetable crops. The result indicated that the highest population of the Aphid was recorded in okra crop (116.13 adults) and the lowest was on eggplant (0.6 adults). Similar data about the population of H. variegate showed that okra plant has the highest density (0.86 adults) compared to potato. 4